1. Field of the General Inventive Concept
The present general inventive concept relates to an inkjet printhead, and more particularly, to an ink feedhole of an inkjet printhead and a method of forming the same.
2. Description of the Related Art
An inkjet printhead is an apparatus for forming an image with predetermined colors by discharging minute ink droplets on desired locations of a printing medium. Inkjet printheads may be classified into two types according to a discharging mechanism of ink droplets. A first type is a thermal inkjet printhead that ejects ink droplets by the expansive force of bubbles generated in ink by a heating source, and a second type is a piezoelectric inkjet printhead that ejects ink droplets by applying pressure to ink via deforming a piezoelectric substance.
The discharging mechanism of ink droplets in a thermal inkjet printhead will now be described in detail. When a pulse current flows through a heater formed of resistance heating elements, heat is generated in the heater, and thus, ink adjacent to the heater is quickly heated up to about 300° C. Accordingly, the ink boils and thus bubbles are generated. The generated bubbles expand, and pressurize an ink chamber filled with ink. Consequently, ink near a nozzle is ejected outside of the ink chamber as droplets. The inkjet printhead may have a structure in which a chamber layer and a nozzle layer are sequentially stacked on a substrate. Here, the substrate is generally formed of silicon. The chamber layer includes a plurality of ink chambers filled with ink to be discharged, and the nozzle layer includes a plurality of nozzles discharging ink. Also, an ink feedhole that supplies ink to the ink chambers penetrates the substrate.
Examples of a method of forming an ink feedhole of an inkjet printhead include a method of wet-etching a substrate and a method of dry-etching a substrate. In the method of wet-etching a substrate, a wet-etching process is performed on a surface of the substrate at an inclination of about 54.7°, and thus a width of an ink feedhole penetrating the substrate may be up to about 5 times wider at a rear surface of the substrate than at a front surface of the substrate. Accordingly, a relatively large area of the substrate is removed during the wet-etching process, and thus hardness of an inkjet printhead including the ink feedhole formed via the method of wet-etching a substrate may decrease. Meanwhile, in the method of dry-etching a substrate, a dry-etching process is performed in a perpendicular direction with respect to a surface of the substrate, and thus an ink feedhole having a uniform width may penetrate the substrate. Accordingly, when dry-etching, an area of the substrate that is etched is smaller than that formed in the method of wet-etching a substrate and thus hardness of an inkjet printhead increases. Also, in an inkjet printhead including a uniform width ink feedhole, bubbles generated by heat from a heater may be trapped in the ink feedhole having a narrow width while discharging ink, and thus it may be difficult to discharge the trapped bubbles. Such trapped bubbles may prevent ink from moving from the ink feedhole to an ink chamber, and thus a discharge characteristic may deteriorate.